The invention relates to electrical power supply circuits.
There is often a need to control the power supplied to an electrical load especially if the power has to be limited or varied in accordance with operating requirements. The present invention has been developed to control the power being supplied to an ohmic heater, such as described in UK Patent Specification 2068200, but can be used for supplying a wide variety of electrical loads. In many cases the supply must be controlled to respond quickly and evenly to changes and also to comply with various regulations of power utility companies so as not to interfere with the power being supplied to other consumers from the same mains supply by the generation of unacceptable harmonics in the mains power supply.